An unhinged man wearing a purple priestly vestment robe and no pants was arrested over the weekend for vandalizing a Manhattan shrine to the first American Catholic saint, cops and witnesses say.

Walter Chisolm, 42, broke into Our Lady of Rosary Catholic Church through a window Saturday morning and entered its shrine to Saint Elizabeth Ann Seton, where he damaged a large crucifix, according to police and photos.

A volunteer at the State Street church discovered the trespasser but was run off by Chislom, as were other workers, a witness said.

“This is my house,” the man was heard muttering to staffers as he chased them out of the building, according to witnesses.

He was then found pacing back and forth on the church’s steps while in the robe and holding a bottle of wine and a statue of the Virgin Mary, police and witnesses said.

He attacked a responding officer around 11:20 a.m., striking him the the face, causing minor injuries, according to the NYPD.

Chisolm was charged with assault on a police officer, burglary, criminal mischief, resisting arrest and obstructing governmental administration, cops said.

It was not immediately clear if the suspect was taken to jail or for a mental-health evaluation, police said.

Seton was the first person born in the US who was canonized by the Catholic Church.

The daughter of a prominent Manhattan couple, she founded the nation’s first Catholic girls’ school and congregation of religious sisters in Maryland in 1810.